In the field of hydraulic, oil or gasoline pumps for internal combustion engines, pistons are generally actuated using rotating camshafts, the cams of which cooperate with cam followers. The cam followers generally comprise a roller articulated on a shaft mounted on the piston, which is suitable for sliding in a bore with which the cam follower forms a transmission element. The bore may be a chamber of a pump body. The shaft on which the roller is articulated is freely translatable along its longitudinal axis and is capable of coming into contact, or not coming into contact, with a wall of the bore in which the piston is mounted.
To avoid deterioration of the ends of the shaft or the surface of the bore, it is known from U.S. Pat. No. 7,793,583 to provide the ends of the shaft with curved surfaces suitable for coming into contact with the bore. Such a solution involves high friction and rapid wear of the bore.
It is known to stop the shaft axially relative to the piston, for example using elastic rings. It is also known to apply a coating on the ends of the shaft, in order to dampen the impact that may occur between the ends of the shaft and the bore. The production of a coating or placement of elastic rings requires additional production steps and creates a significant excess cost.
The invention aims to resolve these drawbacks by proposing a new transmission element whereof the cam follower has a structure allowing the damping of any impacts between the ends of the shaft and the bore more reliably and cost-effectively than in the state of the art.
To that end, the invention relates to a transmission element for an actuating system integrated into an internal combustion engine comprising a cam follower including a roller articulated on the shaft mounted on a piston suitable for sliding in a bore formed in a body of the transmission element, the shaft comprising a body extending around a longitudinal axis. This transmission element is characterized in that the shaft comprises at least one sacrificial tip attached on one of the ends of the body of the shaft and in that the sacrificial tip is made from a material having a hardness below the hardness of the material of the body defining the bore.
Owing to the invention, the potential friction between the ends of the shaft and the bore is damped by the sacrificial tips, which may deteriorate in contact with the bore without causing a failure on the cam follower. Furthermore, their hardness below that of the body defining the bore makes it possible to avoid damage on the surface of the bore.